Rumble strips are commonly found on highways across the country. They are an effective way to prevent accidents and keep drivers alert. Typically, rumble strips are installed in the asphalt of the roadway, becoming part of the road. The rumble strips are grooves in the road, commonly in the shoulder lane of the road, that cause a vibration as a vehicle travels over them. This type of rumble strip, known as a shoulder rumble strip is placed just beyond the travel way to warn drivers they are entering a part of the roadway not intended for routine traffic use. The tires of a vehicle passing over the rumble strips drop into the grooves, which causes tire noise and vehicle vibration.
Generally, there are four types of rumble strips used on roadways; milled, rolled, formed and raised.
Milled rumble strips are the most common type of rumble strips because they can be used on new or existing roads. Milled rumble strips are made by cutting or grinding into the pavement surface with a machine having a rotary cutting head, which creates a smooth, uniform, and consistent groove into the road shoulder. The tires of vehicles that travel over the milled rumble strips drop into the grooves creating tire vibration and noise.
Rolled rumble strips are rounded or V-shaped grooves that are pressed into hot asphalt pavements and shoulders when the surface is compacted. The strips are made by a roller with steel pipes welded to drums, which make the depressions as they pass over the hot pavement.
Formed rumble strips can have similar shapes as rolled rumble strips, but are made by pressing forms into concrete shoulders as they are being constructed.
Raised rumble strips are rounded or rectangular markers or strips that permanently adhere to new or existing pavements. Their height can range from 6 mm to 13 mm, and therefore the use of raised rumble strips is usually restricted to climates where snow removal is not required. Raised rumble strips are typically made from raised humps of asphalt, but can be made from a variety of materials.
These rumble strips generally serve to alert a driver who drifted into the shoulder. As the tires of a vehicle ride over the rumble strips a vibration alerts the driver that they have crossed out of the lane into shoulder.
Typically, permanent rumble strips have no color for visibility or reflectors and are subject to weather deterioration after years of wear. Additionally, they are costly to repair. Generally, all permanent rumble strips hold water and deteriorate from weather, particularly on concrete roads because of pockets that form in the pavement.
Rumble strips can also serve as a warning for road construction or a disabled vehicle ahead. Typically, due to the temporary nature of road work or an accident, permanent rumble strips would not be cost effective or practical. In a work zone, a portable rumble strip would likely be used for the duration of the project. Currently, temporary or portable rumble strip are in the form of raised strips that are applied to a roadway with a weighted roller. One side of the strips has an adhesive backing to adhere to the road, while the opposite side is raised to cause a vibration in a vehicle passing over the strips. Several strips are typically applied in a row to create a vibration when passed over. These portable rumble strips are time consuming to apply and therefore would not be practical for use in an emergency situation. Further, a weighted roller is needed to apply the strips which makes them unreasonable for use by a lay person.
Although rumble strips are becoming more common on roadways, the majority of roads do not have them. According to 2003 report issued by the United States Department of Transportation, Federal Highway Administration, fifty nine percent of vehicle fatalities are due to vehicles that run off the road. Rumble strips are an effective way to reduce this statistic.
In addition, according to the same report above, over 1,000 people are fatally injured in work zone vehicle accidents each year, and over 40,000 people are injured each year as a result of vehicle crashes in work zones in the United States. Rumble strips are not on every road, therefore their benefits are not as widely utilized as possible. The number of accidents can be reduced if rumble strips could be used by any traveler, and in every work zone.